Electricity is currently distributed through a wholesale electrical transmission network or power grid. Typically, the network is operated at a higher voltage than the standard voltage for retail consumption. Electricity may be generated at various locations on the grid by various types of power sources, including nuclear generators, coal-fired and gas driven generators, and hydro electric generators, from where it flows across the grid to centres of demand which include retail distribution operations of for example, local utilities that transmit the electricity onto retail customers, utility operations that distribute electricity to industrial or large commercial customers, or to such large industrial or large commercial customers directly. The form of electrical power that is transmitted over the long distance portions of the grid is alternating current (AC) at high voltage and it is stepped down to progressively lower voltages as it approaches a portion of the grid where it is to be consumed by the end user. An alternative form of current is high voltage direct current (HVDC) which must be inverted back to AC before distribution to the end user. The electricity is directed over a series of electrical wires, supported by power pylons and hydro poles and is often collectively referred to as the power grid. Significant line losses are a feature of such systems.
The development of the grid is often organic in nature. When power supply, power demand and transmission capacity grow at different rates in different locations the potential arises for an excess of supply or demand with an insufficient transmission capacity to move the electricity from one location to another. Changing population demographics and industry locations exacerbate this problem over the long term. Local grid expansion due to local utility planning, and regional grid control, in the form of regional independent system operators also contributes to a lack of a coordinated overall design. The change in the location of consumption and in the location of power generation can result in congestion in the grid at certain points, which can prevent a load centre from receiving enough power. Typically, in North America, this congestion is regional since the wholesale grid is comprised of a relatively small number of large transmission lines. Thus a bottleneck at one location results in supply issues for much of the area on the demand side of the bottleneck (i.e. a big city) that is unable to readily access power from another main transmission line being too remote therefrom. One means currently used for resolving congestion is to allow the market to place a price on the power traversing in the congested region on the grid. During periods of greater demand, a higher price can be obtained for the sale of the power through that bottleneck. The higher price can provide the signal for a degree of demand curtailment.
Electrical demand fluctuates during the day with peaks most often occurring from 8:00 to 10:00 AM and from 5:00 to 8:00 PM. On the other hand, certain types of low cost power generation are more efficient when operated on a continuous basis and other more expensive forms of power generation can be operated in response to peaks and demand. The low cost types of power generation have historically been less attractive to locate sites near population centres (which are typically also demand centres) due to transportation costs associated with the fuel used to generate the electricity, concerns about pollution, and fear of locating nuclear plants near population centres. In the absence of congestion at specific bottlenecks, prices near to low cost generation and a distant load centre are similar but with congestion, and a local excess of demand over supply, price differences can expand significantly. As a result, electricity prices are both time dependent and location dependent in the current power grid. Construction of additional transmission capacity is often not an easy, cost effective or adequate solution to reducing congestion because of the uncertainties of future demand. If new routes are required, then it can be very difficult and expensive to secure the necessary land rights to establish an easement to run the power lines.
Different sections of the grid may be operated by different entities called Independent System Operators. This exacerbates the problems of maintaining an overall grid design as the grid tends to be designed in a piecemeal fashion. The grid operators use several means to control the quantity, quality and stability of the power being transmitted so that the supply is reliable for the customer. The quantity of power transmitted is managed by a system of scheduling and coordinating power transactions between suppliers and consumers which includes managing congestion and/or providing a marketplace whereby rights to traverse a congested part of the grid are exchanged. The quality of power is also in part managed by having generators provide reserves of generation that can be called into service at short notice. The quality of power, in particular the frequency of AC current on the grid, is managed by having suppliers provide spinning reserves that can be called upon instantaneously to help adjust the frequency of the power on the grid or to replace off frequency power supplies. Finally, grid operators also manage the voltage of the AC current on the grid through the provision of voltage support by suppliers to the electrical grid.
Included among these power management strategies are for example, the known technique of peak shaving. In peak shaving, adjacent to a congested location, electricity may be drawn off the grid and locally stored during a low demand period, and then released from that location during a high demand period. Excess demand which is unable to be met due to the congestion at the transmission bottleneck can be met with a boost of locally stored power. While providing an interim or temporary solution, this approach of time shifting does not adequately address the full dynamic nature of the need to match demand to supply through the congested infrastructure of the power grid. As demand grows, the problem of congestion becomes ever more of a concern, a constraint on efficient distribution of electrical power, and inevitably a higher cost to the end user.
As well, as newer renewable resources of energy are tapped, they may be located in sites which are remote from conventional power grids. Indeed, for wind farms and the like, being remote is often preferred.
Efforts exist in the prior art to resolve power grid issues. For example, U.S. Pat. No. 5,610,802 describes an energy storage system which is in a housing having a number of doors and internal racks. Battery modules are placed on the racks and the storage system has an energy storage capacity of 100 kw, and a footprint of less than 400 square feet. This patent describes how the energy storage system is transportable and can be deployed to specific locations to deliver a power boost to a system that is stressed, for example, by extreme cold weather.
However, referring to column 15, line 55 this patent teaches that the batteries be removed and transported separately from the housing during transportation, to reduce the shipping weight of the storage system. It is also contemplated that the batteries be shipped dry, and that the electrolytes be shipped later. So, this patent teaches moving the housing, moving the battery cases separately from the housing and then moving the electrolytes separately from the rest. In other words the invention can be moved from place to place, but is intended to be charged from and discharged at the same location. As such it cannot deal with bottlenecks in the electrical grid.
U.S. Pat. No. 6,026,349 is interesting because it teaches ways to convert and store energy other than through electricity (i.e. compressed gas). However, in this invention teaches locating the storage/discharge facility at the margins of two adjacent power grids, so the energy can be removed from or added to either adjacent grid. The purpose of this invention is to permit specific power conditioning, suitable for either one or the other grid to be performed, to permit the stored power to be released to the power matched grid. However this stationary storage plant cannot be used to for example overcome local bottlenecks in either of the adjacent power distribution grids.
U.S. Pat. No. 6,900,556 is also interesting in teaching the use of capacitors to temporarily store electrical energy. In this patent they teach using a large-scale, capacitor-based electrical energy storage and distribution system capable of effectuating load-leveling during periods of peak demand on a utility, and of effectuating a cost savings associated with the purchase of electrical energy. In a stationary or fixed plant location (for a matter of days or weeks) embodiment a capacitor or multitude of capacitors may be charged with electrical energy produced by the utility, such as during periods of low demand or low cost, and discharged during periods of high electrical energy consumption or high electrical energy cost. One or more capacitors may be located at a consumer's residence or business. Alternatively, a farm of capacitors may be provided at or near a utility, or at or near a location experiencing high demand.
In another embodiment, one or more capacitors may be located in or on a vehicle, such as an automobile, a truck, or a train of a light rail system.
In this embodiment the patent teaches using the stored energy on the vehicle, to drive the vehicle from place to place, for example to permit a light rail line which does not need a power transmission line along its length, therefore reducing the capital cost of the transportation system, (see column 11, lines 5 to 8). In some cases the electrical energy can be applied to a load in the source, but applying the energy to a load does not overcome bottle necks in electrical distribution networks, by making more electricity available on the other side of a bottleneck, which would require power conditioning means to make the electrical energy suitable for adding to the grid at that point. Furthermore, by consuming electrical energy to drive the vehicle, there will be little left over to provide at the load.
Other prior art patents of general interest in power storage and energy distribution include U.S. Pat. Nos. 3,682,704; 5,439,757; 5,798,633; 6,475,661; 6,649,289; 6,653,749; 7,199,550; and U.S. Publication No. 2004/0197649.
What is desired is a form of resolving problems of getting electricity from a location where it can be generated at a low cost, and delivering the electricity beyond the congestion bottlenecks or infrastructure gaps to where it can be sold for a high price. What is required is a way of providing such electricity which is dynamic and can be adapted for changes in the demand location over time without requiring expensive capital improvements to the existing grid, without requiring new expensive right of ways, and without exposing people to more incident electro-magnetic fields associated with high tension electrical wires.